The present invention is related generally to the field of orthodontics, and more particularly to a system and a method for gradually repositioning teeth.
A fundamental objective in orthodontics is to realign a patient""s teeth to positions where the teeth function optimally and aesthetically. Typically, appliances such as braces are applied to the teeth of the patient by a treating orthodontist. Each appliance exerts continual forces on the teeth which gradually urge the teeth toward their ideal positions. Over a period of time, the orthodontist adjusts the appliances to move the teeth toward their final destination.
The process of attaching the braces to teeth is tedious and painful. Additionally, each visit to the orthodontist is time consuming and expensive. The process is further complicated by uncertainties in determining a final arrangement for each tooth. Generally, the final tooth arrangement is determined by the treating orthodontist who writes a prescription. Traditionally, the prescription is based on the orthodontist""s knowledge and expertise in selecting the intended final position of each tooth and without a precise calculation of forces being exerted on the teeth when they contact each other.
The invention provides a method for defining a fit for a set of upper and lower teeth in a masticatory system of a patient. The fit is defined by generating a computer representation of the masticatory system of the patient and determining an occlusion from the computer representation of the masticatory system using one or more keys.
Implementations of the invention include one or more of the following. The key can be selected from a group consisting of a molar relationship, a crown angulation, a crown inclination, teeth rotations, teeth contact points, and an occlusal plane. Where the key is based on a molar relationship, a first permanent molar may be occluded with a second permanent molar. Where the first permanent molar has a disto buccal cusp with a distal surface and the second permanent molar has a mesiobuccal cusp with a mesial surface, the distal surface can occlude with the mesial surface. The mesiobuccal cusp can occlude in a groove between mesial and middle cusps of the first permanent molar. The mesial surface can approach the distal surface. Moreover, the canines and premolars of the teeth have a cusp-embrasure relationship buccally and a cusp-fossa relationship lingually.
Where the key is based on an angulation of a crown, the method can determine a distal inclination of a gingival portion of the crown. The distal inclination can be held constant for all teeth or can be constant within each tooth type. The angulation can be determined between a facial axis of the clinical crown (FACC) and a line perpendicular to an occlusal plane. The angulation can be minimized, positive or negative in value.
Where the key is based on a crown inclination, the method can determine an angle formed by a line perpendicular to an occlusal plane and a line tangent to a bracket site.
The crown inclination can be negative when measured from an upper canine through an upper second premolar. The crown inclination can be progressively more negative when measured from a lower canine through a lower second molar. The crown inclination can be between a line parallel and tangent to a facial axis of the clinical crown (FACC) at its midpoint and a line perpendicular to an occlusal plane.
The key can be based on tooth rotation, or on positions where the teeth are free of undesirable rotations. The key can be based on a tooth contact point, where the contact point can be tight, where no spaces exist between contact points. The key can be based on an occlusal plane. The plane can range between flat to curves of Spee. The curve of Spee can be deep, slight, or reversed.
The method also includes optimizing a final placement of the teeth. The method can also include identifying one or more features associated with the teeth; and generating a model of the teeth based on the identified features. The features can be identified automatically or by a user. The computer representation can be an ideal model set of teeth which can be derived from a cast of the patient""s teeth or from a patient with a good occlusion. The method also includes generating progress reports associated with the determined occlusion. Generated reports can be browsed over a network such as a wide area network (the Internet) or a local area network. The progress report can be viewed by a patient or a clinician. The user, which can be a clinician or a patient, manipulates the computer representation of the masticatory system.
The method also includes generating a model the teeth; and adjusting teeth position in the model by following a prescription. The method further includes generating a model of the teeth, the model having a visual appearance; and adjusting teeth position in the model until the visual appearance of the model is satisfactory. The model can be based on an abstract model of idealized teeth placement. The abstract model can be specified by one or more arch forms, or can be specified using one or more features associated with the teeth. The teeth position can be customized to the patient""s teeth.
In another aspect, a system for generating one or more appliances for a patient includes a processor; a display device coupled to the processor; a data storage device coupled to the processor; a scanner coupled to the processor for providing data to model the masticatory system; means for defining a fit between a set of upper and lower teeth in a masticatory system of the patient; and a dental appliance fabrication machine coupled to the processor for generating the appliances in accordance with the fit of the teeth.
Advantages of the invention include one or more of the following. When a prescription or other final designation is provided, a computer model can be generated and manipulated to match the prescription. The prescription may be automatically interpreted in order to generate an image as well as a digital data set representing the final tooth arrangement.